Kind/book/List.length.kind2
2024-03-01 20:40:31 -03:00

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List.length
: ∀(A: *) ∀(a: (List A)) Nat
= λA λa
let P = λx Nat
let cons = λa.head λa.tail (Nat.succ (List.length A a.tail))
let nil = Nat.zero
(~a P cons nil)